Lacteous is an adjective that refers to something that is milky or resembling milk in color, texture, or composition. Its antonyms would therefore be words that describe things that are not milky, such as clear, transparent, or colorless. Other antonyms for lacteous might include words that describe things that are dry or powdery, like desiccated or parched. Alternatively, one could offer antonyms that are more opposite in meaning, such as words like dirty, murky, or polluted. Ultimately, the choice of antonyms will depend on the context in which the word lacteous is being used, as well as the intended emphasis of the writer or speaker.